Conventionally, an ejector-type refrigerant cycle device having an ejector, provided with functions of a refrigerant decompression means and a refrigerant circulating means, is known. For example, Patent Documents 1-3 describe regarding an ejector-type refrigerant cycle device, in which refrigerant discharged from a compressor is cooled by performing heat exchange with outside air in a radiator, and the cooled high-pressure refrigerant is decompressed in a nozzle portion of an ejector.
For example, in an ejector-type refrigerant cycle device of Patent Document 1 (JP Patent No. 3322263 B1 corresponding to US 2001/0025499 A1), a gas-liquid separator is arranged at a downstream side of a diffuser portion of an ejector to separate low-pressure refrigerant into gas refrigerant and liquid refrigerant. Furthermore, a gas refrigerant outlet of the gas-liquid separator is connected to a refrigerant suction port of the compressor so that gas refrigerant separated in the gas-liquid separator is drawn to the compressor, and a liquid refrigerant outlet of the gas-liquid separator is connected to a refrigerant inlet of a suction side evaporator so that liquid refrigerant separated in the gas-liquid separator is evaporated in the suction side evaporator and the evaporated refrigerant is drawn into the ejector from a refrigerant suction port of the ejector.
In an ejector-type refrigerant cycle device of Patent Document 2 (JP Patent No. 3931899 B2 corresponding to US 2005/0178150 A1), a branch portion is provided at an upstream side of a nozzle portion of an ejector to branch a flow of the refrigerant flowing out of a radiator. Furthermore, the branch portion is provided, such that one refrigerant branched at the branch portion flows toward the nozzle portion of the ejector, and the other refrigerant branched at the branch portion flows toward a refrigerant suction port of the ejector via a suction side evaporator.
In an ejector-type refrigerant cycle device of Patent Document 3 (JP 2008-107055A corresponding to US 2008/0098757 A1), a branch portion is provided at a downstream side of a diffuser portion of an ejector to branch a flow of the refrigerant flowing out of the diffuser portion. Furthermore, the branch portion is provided, such that one refrigerant branched at the branch portion flows toward a compressor via a discharge side evaporator, and the other refrigerant branched at the branch portion flows toward a refrigerant suction port of the ejector via a suction side evaporator.
In the ejector adopted to the above ejector-type refrigerant cycle devices, refrigerant is decompressed and expanded in the nozzle portion of the ejector in iso-entropy, and the refrigerant downstream of the suction side evaporator is drawn into the ejector from the refrigerant suction port by the refrigerant suction action due to a high-speed refrigerant jetted from a jet port of the nozzle portion, thereby recovering the loss of the kinetic energy in the decompression and expansion of the nozzle portion.
By converting the recovered kinetic energy to the pressure energy in the diffuser portion of the ejector, the pressure of the suction refrigerant of the compressor can be increased, thereby reducing the driving power of the compressor and improving the coefficient of performance (COP) in the ejector-type refrigerant cycle device.
In the above refrigerant cycle device, the refrigerant flowing out of the suction side evaporator is drawn into the ejector from the refrigerant suction port, so as to improve the COP. Thus, in order to improve the COP due to the ejector, it is necessary to sufficiently draw the refrigerant flowing out of the suction side evaporator from the refrigerant suction port of the ejector by using the refrigerant suction action.
Furthermore, in the ejector-type refrigerant cycle device, it is necessary to suitably adjust a refrigerant circulation amount in accordance with a cooling capacity or a heating capacity required in the ejector-type refrigerant cycle device.
However, if a refrigerant discharge capacity of a compressor is reduced in accordance with the cooling capacity or the heating capacity required in the refrigeration cycle device, a pressure difference between a refrigerant pressure at a refrigerant inlet side of the nozzle portion of the ejector and a refrigerant pressure at a refrigerant outlet side of the nozzle portion of the ejector is reduced, thereby reducing a flow speed of the jet refrigerant jetted from the nozzle portion. As a result, it is difficult to sufficiently draw the refrigerant flowing out of the suction side evaporator from the refrigerant suction port of the ejector, and thereby it is difficult to effectively improve the COP by using the ejector.